The objective of this work is to dissect the role of protein LYT1p in T. cruzi development and pathogenesis. This protein was first identified in the lab of Antonio Gonzalez (Spain) who found it by screening a cDNA library with antibody directed to the mammalian C9 component of complement. LYT1 is a single copy gene that is dispensable in T. cruzi epimastigotes. However, LYT1 deficient parasites have three phenotypes: 1) they are infection deficient; 2) they exhibit accelerated in vitro development; and 3) they have diminished hemolytic activity. There are two main goals in this project: 1) to understand how the LYT1p is involved in the biological processes leading to human infection; and 2) to use LYT1p deficient parasites to identify stage specific genes involved in parasite development.